Download Part 1 Identify Type of Output Module

Electrical and Electronic Engineering Department
ELEG3243 Programmable Logic Controllers
PLC Laboratory 3
Output Module and Basic Ladder Diagram
Name:
Due Date:
Submission Date:
Lecturer:
25 Sep 2015
Tan Teck Siang
OBJECTIVES
1. Identify the output module of the Mitsubishi FX-series and OMRON PLCs.
2. To make students familiar with the various types of modules.
3. To learn the basic of ladder diagram.
EQUIPMENT AND SUPPLIES
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7.
Mitsubishi FX-20MR PLC
OMRON OC211 Output Module
Toggle Switches
Breadboard
Input Extension
PC with Mitsubishi PLC Programmer
10W Power LED
INTRODUCTION
As with input modules, output modules rarely supply any power, but instead act as switches. External power
supplies are connected to the output card and the card will switch the power on or off for each output.
These cards typically have 8 to 16 outputs of the same type and can be purchased with different current
ratings. A common choice when purchasing output modules is Relays, Transistors or Triacs. Relays are the
most flexible output devices. They are capable of switching both AC and DC outputs. But, they are slower
(about 10ms switching is typical), they are bulkier, they cost more, and they will wear out after millions of
cycles. Relay outputs are often called dry contacts. Transistors are limited to DC outputs, and Triacs are
limited to AC outputs. Transistor and Triac outputs are called switched outputs.
Figure 3-1 shows the typical wiring for the DC and AC output modules.
a. Triac Output Module
b. Relay Output Module
c. Transistor Output Module
Figure 3-2 shows the typical internal circuits of various types of output modules.
LADDER LOGIC DIAGRAM
There are various methods of programming a PLC. Two of these include Ladder Logic and Function Block
Diagrams. The choice of which method is dependent on whether the operation being automated is machine
control or process control oriented. Ladder Logic is the method of choice in the case of machine control and
Function Block for process control.
Figure 3-3 Ladder Schematic
Electricians are familiar and comfortable with ladder schematics, see Figure 3-3. These diagrams depict two
vertical lines called rails. The rails provide power to the circuitry of the schematic. The power can be AC
or DC and the voltage may vary depending on the requirements. Standard labelling for rails is L1 and L2.
Circuitry is placed between the rails connecting the two power lines. These individual lines are referred to
as rungs. The circuitry is typically very specific for ladder schematics. For instance, in the following
diagram note the first rung consists of a start button that is actually a momentary switch.
Inputs
Outputs
Figure 3-4 Ladder schematic with push button and relay
Rungs are composed of inputs and outputs (refer to Figure 3-4). If an imaginary line is drawn down the
middle of the previous diagram all the inputs (switches, etc.) are located to the left. Outputs are located to
the right. Locating all inputs on the left side of a rung and all outputs on the right is good design practice but
not required.
Outputs from a PLC are referred to as coils on a ladder diagram. A coil may represent a motor, light, pump,
counter, timer, relay, etc. The following displays how a coil is represented in a ladder diagram.
Figure 3-5 Coil representation in a ladder diagram
Inputs/Sensors to a PLC are referred to as Contacts and may consist of switches, buttons, etc. Contacts
begin in one of two states normally open or normally closed. A graphical representation of a normally open
and closed contact is depicted as it would appear in a ladder diagram.
Figure 3-6. Normally-Open and Closed representation in a ladder diagram.
PRODECURE
Part 1 Identify Type of Output Module
1. Observe the output modules of the Mitsubishi FX-14M, FX-20MR and OMRON OC211 PLC.
2. Record down the type of each output module.
3. Sketch the wiring diagram for these two output modules. Record down the actual output pin, supply
voltage and etc.
Observations:
Part 2 Solving for Logic Function
1. Develop a program that will cause output D to go true when switch A and switch B are closed or
when switch C is closed.
2. Construct the truth table and write the logic function for (1).
3. Sketch the logic diagram for (2).
4. Sketch the ladder diagram for (3).
Observations:
Part 3 Wiring the Output Module
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Use two toggle switch for switch A and B in the part 2 and the reed switch for switch C.
Connect switch A, B and C to the output module of FX-20MR PLC.
Connect the 10W LED to output Y0
Sketch the wiring diagram in the space below.
Record down your observations.
Observations:
Part 4 Program the PLC
1. Launch the FXGP programmer.
2. Open a new file and select the FX series.
3. Locate the input/output toolbar and draw the ladder diagram you have obtained from part 3.
4. Record down the instruction for the ladder diagram.
5. Convert the ladder diagram, go to Tools >> convert.
6. Change the PLC into “Programming” mode.
7. To Program the PLC, go to PLC >> Transfer >> Write. Select “All range”.
8. Change the PLC back to “Run” mode.
9. Verify the result by changing the state of the switches and observe the output.
Observations:
QUESTIONS
1. What is the typical response time for the Relay Output Modules?
2. What is the typical response time for the Transistor Output Modules?
3. What is the typical response time for the TRIAC Output Modules?
4. How long is the service life of the mechanical and electrical parts o f a relay?
5. What is the main factor that influences the service life of relays?
6. What is the current and voltage rating for Transistor, TRIAC and Relay Output Modules?